1. Field of the Invention
This invention relates generally to the process for forming resinous composition surface coverings and more particularly to an "upside-down" process for forming such a product wherein a resinous dryblend layup is formed on a release carrier and heated to form a porous cohesive layer. Settable resinous inks are applied to and set within the dryblend layer to create design areas thereon which may overlap on the surface to which they are applied. The design elements may extend through the thickness of the layer from the back thereof to form a sharply defined non-overlapping wear layer design, or some of the design elements may extend only partially through the dryblend layer to create an appearance of depth in the design when viewed from the wear surface of the sheet after inversion thereof. If desired, a permanent carrier may be applied either prior to or subsequent to a final fusion of the structure and removal of the release carrier. The product is then inverted for use.
2. Description of the Prior Art
It is known to enhance the appearance of plastic floor and wall coverings by means of various decorative designs thereon which may extend partially or entirely through the sheet. It is also known to form a decorative surface covering by applying a resinous coating to a releasable carrier, decorate the coating, apply the backing and then remove the releasable carrier and invert the product for use.
One method for producing a through-grained pattern on a flexible floor covering is shown by U.S. Pat. No. 592,186 wherein granular linoleum-forming material is preconsolidated on a backing sheet at a slightly elevated temperature to form a porous mass. The partially consolidated mass is then printed by means of printing blocks or rollers so that the colored or inlaid effect penetrates to a greater or lesser extent the substance of the linoleum. The sheet is then fully consolidated by heat and pressure.
U.S. Pat. No. 3,359,352 describes depositing a layer of fine granules of resinous composition on the surface of the base, heating to sinter the granules and form a porous layer, printing a design on the sintered layer with a printing composition which will penetrate into the porous composition and then, by heat, with or without pressure, forming the printed porous layer into a non-porous layer containing an inlaid design.
Another method of forming a decorative thermoplastic resinous sheet is shown by U.S. Pat. No. 2,874,416, wherein a thin layer of thermoplastic resin is applied to a carrier sheet; a design is printed on the resinous sheet before any film strength is developed therein; a body layer of a thermoplastic resin is applied over the printed design; the layers are fused by application of heat thereto; and, the resulting decorated sheet is stripped from the carrier.
British Pat. No. 658,530 relates to a process for making decorative polyvinyl resin sheets. The process comprises printing on a support, a design in colors, each formed of a suspension of a polyvinyl resin and a pigment in one or more plasticizers. The various colors of the design flow together to form an unbroken sheet wherein the design elements extend compltely through the thickness thereof.
Prior methods of forming a decorative wear surface on resinous composition surface coverings utilizing dryblend material involved printing on the surface of the dryblend layer which ultimately became the wear surface of the finished product. Because the inherent spreading of ink when printed on a dryblend is greatest at the points of application, there has existed in the prior art the problem of the need to print in register and yet obtain clearly defined design boundary lines. It has been especially difficult in the past to accomplish the foregoing where it was desired to have design elements extend clear through the thickness of the sheet, since this required that a relatively larger amount of ink be applied and therefore more spreading of the ink would occur on the surface of the sheet at the points of application resulting in overlapping and blurring of the design elements at their boundary lines. This is the problem which is solved by the process of this invention.